Generally speaking, there are many ways to provide warning marks which separate traffic lanes on roads. The most common and simplest way is to apply a coating of white, yellow or red paint to the road surface, which can be an asphalt pavement, in accordance with the appropriate color for the type of warning desired. Because these marks are not always visible or clear to drivers, particularly at dangerous turns, at night, on rainy days and in heavy fog, they cannot provide an appropriate safety warning function In addition, the paint coatings will fade after time because of wear by vehicles running over them and deterioration by weather. Therefore, roadstuds having appropriate heights and made from aluminum alloy or plastics are used on the pavements. These roadstuds have front and rear inclined planes in which reflective pieces are inserted to reflect light from a vehicle's headlights, and thus increase the warning effect. Although this product is superior to a paint line for light reflecting properties, it still has many practical drawbacks.
(A) The compressive yield strength of the above-mentioned aluminum alloy or plastics structure are all below one ton. Moreover, the breaking strength is below 3 tons. Therefore, they are easily deformed or fractured by a compressive load. Thus, frequent replacement must be made. Furthermore, it is likely that this type of marker can be punctured.
(B) As the reflective piece of the aforesaid light-reflecting roadstud is externally exposed, it is susceptible to the collection of dust and damage from being crushed, thereby losing its reflective properties in either case.
Considering these drawbacks, a reflective roadstud called "Armor Light" has been developed using tempered glass by South-African Pilkington Company (as shown in FIG. 1 and 2). The roadstud comprises an embedded round, plate part (A) and a semi-spherical protruding part (B). The outside of the embedded part is plated with an aluminum or zinc metal film to form a reflective side mirror (C). The protruding part (B) serves to collect the incident light and focus it on the reflective mirror (C) which in turn reflects the light again and passes it back through the protruding part (B). Hence, this roadstud can condense and reflect the light and look like a bulb in the night. It indeed offers a clear warning to drivers about the position of the separating line on the roads at night and in bad weather. Furthermore, in order to improve the resistance to the impact and wear by vehicles, the glass roadstuds are all subjected to a tempering treatment to increase their strength and surface hardness. On an average, the compressive fracture strength is set at above 20 tons, while that of the glass without a tempering treatment is only around 5 tons.
Though the Pilkington's roadstud using tempered glass can avoid the above-mentioned drawbacks of those roadstuds structurally made of aluminum or plastics, because of the specific composition of the glass, the roadstud has a blue-green color. No matter whether they are used on a white or yellow separating line, they all reflect a green light from a car's headlight. This is not in conformity with the color of the separating lines. In particular, placing this roadstud on the yellow separating lines would easily bring confusion to drivers, and would adversely affect the traffic order.
Due to this Achilles' heel, the glass roadstud has not received broad application on the road until now. Furthermore, since the glass roadstud contains no ingredient which can increase the reflective index and transparency, it has the properties of ordinary window glass. Consequently, the reflecting light intensity is not high and it shows no brilliant effect such as provided by crystal glass or optical glass. If these two properties were improved, it can be expected that the performance of the glass roadstud would increase, especially in bad weather.